There has been conventionally devised a rotation angle detection device, which utilizes a change in permeance of a gap between a rotor and a stator, as a device which is simple in its structure and inexpensive, and at the same time, can withstand even a high temperature environment as opposed to an optical encoder which is limited in its operating temperature environment and is complicated in its structure and expensive. For example, an example of a rotation angle detection device having excitation windings of two phases and a one-phase output winding is described in JP 62-58445 B. In addition, an example of a rotation angle detection device having an excitation winding of one phase and output windings of two phases is described in JP 49-124508 A. In both the examples, since a rotor is formed to have salient poles, a phase or an amplitude of a voltage induced in an output winding changes depending on an angle of the rotor, and a position of the rotor can be found by reading the change. In addition, a rotation angle detection device having excitation windings of three phases is disclosed in Japanese Patent No. 2624747. Moreover, an example in which a winding is concentrically wound around teeth of a stator and the number of turns is changed in a sine wave shape is disclosed in Japanese Patent No. 3103487 and Japanese Patent No. 3182493.
Examples of the conventional rotation angle detection device are shown in FIGS. 73 and 74. FIG. 73 shows, as a conventional example, an example of the rotation angel detection device in which a shaft multiple angle is 1 and the number of teeth of a stator is four, which is the same as the rotation angle detection device disclosed in JP 49-124508 A. On the other hand, FIG. 74 shows an example of the rotation angle detection device in which a shaft multiple angle is 4 and the number of teeth of a stator is sixteen. In those figures, reference numeral 100 denotes a stator; 101, a rotor; 102, four teeth provided in the stator 100; and 103, a winding wound around the teeth 102. In a system of FIG. 73, as the shaft multiple angle increases, the number of teeth also increases in proportion thereto. For example, in the case in which the shaft multiple angle is changed to 4, the structure changes to the one as shown in FIG. 74, the number of teeth increases to as many as sixteen, and winding workability deteriorates. Thus, it can be said that this is a structure not suitable for mass production.
The above-mentioned conventional examples have the following problems. If the winding structures as disclosed in JP 62-58445 B and JP 49-124508 A are adopted, there is a problem in that, in the case in which the shaft multiple angle increases, the number of teeth of the stator also increases in proportion thereto as described above, and a winding property and a machining property deteriorate.
In both of JP 62-58445 Band JP 49-124508 A, the shaft multiple angle island the number of teeth of the stator is four. For example, in the case in which the shaft multiple angle is changed to 2, the number of teeth increases to eight, in the case in which the shaft multiple angle is changed to 4, the number of teeth increases to sixteen, and in the case in which the shaft multiple angle is change to 8, the number of teeth increases to as many as thirty-two. Although a rotation angle detection device with a large shaft multiple angle may be required in a multipolar motor, if the shaft multiple angle is large in such conventional examples, the rotation angle detection device has a structure which is unrealistic in terms of mass productivity.
In the structure as disclosed in Japanese Patent No. 2624747, windings are one phase for output and three phases for excitation. That is, the number of phase is large. Thus, there is a problem of productivity in that winding takes time and a problem in that a power supply for the excitation windings becomes expensive.
In the examples of Japanese Patent No. 3103487 and Japanese Patent No. 3182493, since a winding is wound concentrically around the teeth of the stator, automatic winding by a machine is enabled. However, since the number of turns is changed in a sine wave shape, there are teeth to which only a small number of turns are applied. A nozzle of a winding machine for automatic winding has to be moved to the teeth to which only a small number of turns are applied. Thus, since time is taken for positioning of the nozzle, there is a problem in that efficiency of winding work is low.
The present invention has been made in order to solve such problems, and therefore it is an object of the present invention to obtain a rotation angle detection device with a simple manufacturing process and a dynamo-electric machine using the same.